Parent/Child REST Controller for CRUD

parent.php

// Routing
'api/:parent/:pk/:child/create' => 'api/parent/child',

// controller/api/parent.php
<?php

class Controller_Api_Parent extends Controller_Crud
{
    public function get_child()
    {
        $parent = "Model_Api_Orm_".ucfirst($this->param("parent"));
        $child = "Model_Api_Orm_".ucfirst($this->param("child"));
        
        $parent_model = new $parent();
        $parent_orm = $parent_model::find($this->param("pk"));
        
        $child_model = new $child();
        $child_orm = $child_model->from_array(Input::json());
        $child_orm->save();
        
        return $this->response(array(
            "parent" => array(
                $parent => $parent_orm->to_array(),
                ),
            "child" => array(
                $child => $child_orm->to_array(),
                ),
            )
        );
    }
}